This section is intended to provide a background to the various embodiments of the technology described in this disclosure. The description in this section may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and/or claims of this disclosure and is not admitted to be prior art by the mere inclusion in this section.
Currently, wireless communication networks or systems operating at high frequencies from 10-300 GHz are emerging as a promising technology to meet exploding bandwidth requirements by enabling multi-Gb/s speeds. For example, the 5th Generation (5G) network is likely to be a combination of the evolved 3rd Generation (3G) technologies, the 4th Generation (4G) technologies and emerging or substantially new components such as Ultra-Density Network (UDN).
To meet requirements on dramatically increased traffic, one interesting option for development of the 5G network is to move to new frequency bands which have large amounts of spectrum. Particular bands of interest are the MilliMeter-Wave (MMW) bands of 15-90 GHz. Propagation poses a unique challenge for MMW systems. Besides large scale propagation loss, in reality, at least three factors such as Terminal rotation, obstacles and mobility lead to quick link quality fluctuation at high-frequency radio.
In other sides, some higher requirements are put on the 5G systems. For instance, Critical-Machine Type Communication (C-MTC) may require a high reliability and low delay. That is to say, instead of throughput maximization, robustness enhancement by diversity from multiple points (also referred to as Multiple Point Diversity (MPD) hereinafter) is necessary for the 5G systems, especially when working at MilliMeter-Wave.
FIG. 1 illustrates an exemplary scenario where MPD may be applied.
As shown in FIG. 1, UE1 will establish (at least) two connections with two different access points, AP1 and AP2, and transmit the same data to the network side via the two connections simultaneously. Then, the network side is responsible for collecting the UE1's data from the two access points to get the MPD gain.
FIG. 2 illustrates an exemplary simulation to show a problem of the normal uplink MPD. For sake of explanation, the simulation is made in the scenario as illustrated in FIG. 1, where UE1 transmits data to the network side simultaneously via AP1 and AP2. Connections via AP1 and AP2 are denoted as Link 1 and Link 2, respectively.
As illustrated, before time of t1, Link 1 is much better than Link 2 and most of the data is actually transmitted via AP1. From t1 to t2, Link 2 is better than Link 1. So, from time of 0 to t1, the amount of data that has been successfully transmitted via AP1 is much bigger than that of AP2. From t1 to t2, AP2 receives more data than AP1. Then, from t2, the situation returns to the period from 0 to t1. Therefore, from UE1's point of view, it does not get any gain from this diversity during the period from t1 to t2, because some pending portions of the data are still to be transmitted via AP2. Hereinafter, transmissions of such pending portions of the data may be referred to as pending transmissions.